Interferometry for forest studies

This paper presents the use of ERS-1 repeat-pass interferometric data for forest environment studies. The overall objective is to assess the use of interferometric information - degree of coherence and phase difference - for forest / non-forest mapping and for retrieving forest parameters. Interferometric data acquired over a reference test site of temperate forest (Landes, France) and over a tropical forest site (South Sumatra) have been analysed. Coherence is shown to be a good discriminator between forest stands and bare soil surfaces. However, the conditions for optimal use of coherence depend on the forest and environment characteristics. In the specific case of the Landes forest (flat and homogeneous forest stands), phase difference statistics are shown to be linked to forest stands heights. The knowledge of the penetration depth of the wave into the forest canopy, obtained from theoretical modeling, is shown to be necessary to get a good estimate of stands height from interferometric phase difference.